Vacuum pump



Feb. 16, 1937. J. p. JOHNSON VACUUM- PUMP Filed April 24, 1934 2 Sheets-Sheet 1 W. W V .Mm

Feb. 16, 1937-. J. P. JOHNSON 2,0?0,662

VACUUM PUMP Filed April 24, 1934 2 Sheets-Sheet 2 JNVEN roe.- JAME: JOHNSON mama/aw Patented Feb. 16, 1937 UNITED STATES PATENT OFFICE VACUUM PUMP James P. Johnson, Shaker Heights, Ohio I Application April 24, 1934, Serial No. 122,155 14 Claims. (01'. 230-153 This invention relates to a rotary pump of the -vane or blade typein which the rotor is eccentrically mounted with respect to the chamber within which it rotates and has for its primary object to provide an improved pump of this type which is simple in construction, efiicient in operation, and inexpensive to manufacture.

A further object ofthe invention is to provide- I a pump of the type referred to adapted to create a vacuum or reduced pressure with respect to atmosphere and especially designed for use' on:

aircraft for creating the necessary pressure required' in the operation of various instruments and gauges.

A still further object of the invention is to pro-. vide a means for controlling and varying the amount of pressure created by the operation of the pump.

Another object of the invention resides in providing a pump of the type referred towhich is capable of being operated in opposite directions with equal efiiciency and without the necessity of disengaging or dismantling the pump.

A still further. object of the invention is to pro- 1 vide a pump of thetype referred to which is light in structure, has the required capacity and which will emciently operate under all conditions of flying. v A still further object of the. invention is to provide a novel means for lubricating the movable parts of a pump of the type referred to.

With the objects above indicated and other objects hereinafter explained in view, the invention consists in the construction and combination of elements hereinafter described and claimed.

Referring to the drawings: Figure 1 is a top plan view of a full sized pump embodying the present invention.

.Fig. 2 is a longitudinal sectional view taken on I line 2-2 of Fig. 3.

' which has been designed especially for usein aircraft and is of the vacuum or reduced pressure type employed in connection with the operation of various types of instruments and gauges required in connection with flying. In the first place the weight of the pump and the overall dimensions are of primary importance, because the weight of the plane must be kept as low as possible with respect to the horse power of the motor, in order to obtain the best flying conditions. Pumps for this type of use are required to operate at one and one half times engine speed and are actually tested at speeds up to 5,000 R. P. M. Therefore, the metals of the relatively movable parts of the pump must be light and of such characteristics toprevent seizing and undue wear caused by friction. The structure of the pump and the metals employed in the various elements are therefore of primary importance in providing a pump of high efilciency and still coming within the requirements set forth.

. Referring particularly to Figs. 1, 2, and 3, l0 indicates generally a housing, preferably of aluminum or some similar light weight material, which is open at one end and closed at the opposite end. At the closed end of the housing l0 an axial extension H is provided, preferably formed integral with the housing. and at the free end of said extension there is a laterally extending flange I2, more clearly shown in Fig. '7, having openings l3 provided therein by which the housing may be suitably attached to a portion of the but additionally functions as one of the end walls of the circular opening I4.

A tubular sleeve l1, preferably of hard cast iron, is secured within the circular opening M of the housing and has its inner end abutting the closed end of the housing, .while the opposite 'end is engaged by the cover plate l5, as clearly shown in Fig. 2. The housing I0 is provided with passageways l8 and I9 of identical area disposed on diametrically opposite sides of the housing and normally non-communicating. The sleeve is provided with spaced transverse openings 20 and 2! communicating with the passageway at its opposite extremities, while spaced transverse openings 22 and 23 are provided in the sleeve IT. and communicating with the passageway I9 at its opposite extremities, as clearly shown in Fig. 3. These pairs of. openings are provided in the sleeve l1 so that the pump may be operated in opposite directions without requiring any readjustment of the operating parts. At the upper portion of the housing It) screwthreaded openings 24 and 25 are'provided which communicate with the'upper portions of the passageways l8 and I9, respectively, to permit the pump to be properly connected with the various instruments in a manner well understood.

A rotor 26, preferably made of hardened steel is eccentrically positioned within the sleeve l1 and has a running engagement with the inner. surface of the sleeve H at 21. The rotor, of course, is coextensive with the sleeve IT, as shown in Fig. 2. One end of the rotor 26-is provided with an axial extension 28, preferably formed integral therewith and which is antifrictionally mounted in a ball bearing race 29 contained in the extension I l of the housing, as clearly shown in Fig. 2. The opposite end of the rotor 26 is provided with an axial'extensionSU, preferably formed integral therewith, and likewise is antifrictionally mounted in a ball bearing race 3I contained in a recessed portion 32 provided on the inner side of the'cover plate I5. The extension 36 is provided with an axial opening 33,' which communicates with an axial bore 34 of larger diameterprovided in the rotor 26 for a purpose to be later described, the longitudinal length of the bore, however, being slightly less than the longitudinal length of the rotor 26.

The rotor 26 is provided with a plurality of radially disposed'slots 35 which extend through the wall of the rotor and throughout its length,' there being in this particular construction four of such slots employed, although various numbers may be employed,-depending upon the nature of the pump. The relationship between the length of the bore 34 and the length of the rotor 26 permits the segments of the rotor. between the slots 35 to be integrally united with the extensions 26 and 30, respectively, at opposite ends so as to prevent any tendency for these segments to move outwardly by centrifugal action when the rotor is rotated at high speeds.

Blades 36, preferably of heat-treated aluminum alloy, are disposed, in the slots 35-and have a sliding fit therein. These blades are substantially T-shaped in longitudinal section and have their outer ends formed a'rcuate at 3I,'as shown in Fig. 3, the outer ends being adapted to engage the inner peripheral surface of the sleeve l1 clue to centrifugal action asthe rotor is ro tated. The inner ends 36 of the blades 36 are also formed arcuate and engage with a hollow roller member 39 disposed within the bore 34 of the rotor 26. The opening, in the extension 30 of the rotoris made of suflicient diameter to permit the roller member 39 to be inserted therethrough so as to properly position the roller member in the bore 34 and, due to the fact that the diameter of the bore 341s larger than the diameter of the opening 33, the roller member 33 is prevented from accidental displacement and any appreciable amount 01 longitudinal movement within the bore, at the same time permitting ready access in case it becomes necessary to replace the roller member. I

The rotor 26' is provided with longitudinally extending'openings 46 in the wall thereof between the slots .35 for the purpose of lightening as'muchas possible the weight of the rotor. Likewise, the'blades 36 are provided with a plurality of longitudinally extending openings .4! :gr tn? similar purpose of lightening the weight ereo While the blades 36 are made of an aluminum alloy, principally because of its lightness, it is necessary to lighten the blades to a further extent, which is accomplished, in the present construction, by the provision of the openings 4|.

It should be'noted that there is nothing which secured in an opening 43 provided upon the inner I face of the cover plate l5, the free end extending into the interior of the roller member 39. An opening 44 communicates with the opening 43 in the: cover plate and extends upwardly communicating with a screw-threaded opening 45. This screw-threaded opening may be connected with any suitable source of oil supply available. The hollow roller member 36, is provided with a plurality of openings 46 extending through the wall thereof so that when the lubricant is dis-- charged from the tubular member 42 it will be deposited in the interior of the roller member. Upon rotation of the rotor when the pump is in operation, centrifugal action, will cause the lubricant to flow outwardly between the relatively movable parts and the lubricant may then be carried oif through one of the screw-threaded openings 24 or 25, depending upon the direction of rotation of the motor, to the housing of the motorv The free end of the extension 28 on the rotor 26 has a. bushing 41 secured to the outside thereof which is rotatably mounted in an opening 46 provided in the end of the-extension A packing ring 49 is disposed in a groove provided in the extension and engages the bushing 41 .to prevent the passage of oil thereby. The end of the extension 28'has an axial bore 50 within which is disposed an extension 5| of a T-shaped member 52. Aligned openings are provided through the bushing 41, extension 28, and extension 5| to receive a pin 53 which securelyv main- T-shaped member 52 is adapted to be connected with the motor of the airplane or other suitable means for imparting rotation to the rotor.

As the pump is designed principally to create a reduced pressure and being of the reversible struction'is illustrated wherein this-control means is formed as an integral part of the housing l6.

This consists of an extension 54 provided at the upperportion of the housing adjacent the inlet and outlet openings 24 and 25. The extension is I provided with a pair of axially aligned bores 55 and 56 extending inwardly from the opposite ends I of the extension and spaced apart to provide a transverse partition 51 substantially midway of the length of the extension. These bores 55 and opening 59. The .bores 55 and 56 are, therefore;

in communication with the screw-threaded openings 24 and 25 connected to the operated.

instruments to be 3 With the rotor 26 operating in a clockwise direction the valve mechanism for controlling the amount of air drawn into the pump is contained in the extension 54 adjacent the bore 55. Slidably and loosely mounted in the outer end of the bore 55 is a valve member 68 of non-metallic materialand a materialwhich is light in weight. Slots 6| are provided in the peripheral edge of the valve member, as shown in Fig. 5 to permit ready and A cap 62 is detachablyconnected to the end of the extension by means of bolts 63 and is provided with an axial opening 64 through which air may be drawn from the surrounding atmosphere. A valve seat 65 is provided on the inner surfaces of the cap 62 and extends around the opening, the valve member 68 normally cooperating with the valve seat to control the amount of air drawn thereby. The partition 5! has an axially extending interiorly screw-threaded opening 66 provided therein and amember 61 has an exteriorly screw-threaded portion 68 adjustably disposed in the screw-threaded opening 66. The member 61 is provided with an axial bore 68 extending inwardly from the end adjacent the valve member 68 which receives a coiled spring 18, one end of which abuts the base of the'bore, while the other end extends beyond, the end of the member 61 and into engagement with the under side of the valve member 68 to normally urge the valve. member 68 into engagement with the valve v seat 65. A screen 'H is secured to the cap 62 and vided with a transverse slot 18. Adjacent this end of the extension 54 a cap 14 is provided which is also detachably connected to the open end of the extension by means of bolts I5. The cap 14 1 has a depending extension or tongue 16, preferably formed integral with its inner sideand which is disposed in the slot 13. By removing the bolts 15 the member 61 may be adjusted longitudinally within the screw-threaded opening by turning the cap 16, and the openings to receive the bolts 15 may be placed in any desired spaced relation so as to obtain the desired adjustment. 50

In the event that the rotor 26 should be rotated in a counter-clockwise direction the only change necessary to render the pump operable is to reverse the valve mechanism. By that is meant the cap 62, the valve 68, the member, and the spring 18 are removed, as well as the cap 14 upon the opposite end of the extension. This entire structure then ,is reversed so that the valve operating means is mounted on the opposite end of the extension from-that shown in Fig. 4, with the valve member 68 slidably disposed in the bore 56. In Fig. 8 a modified form of rotor is shown which may be substituted in place of the rotor 26 shown in the otherhgures of the drawings, but it should be understood that the other parts of the pump structure remain the same and operate in the same manner.

It maybe desirable to provide a-pump structure in which there is practically no chance for any foreign matter accumulating between the rotor and that portion of the liner with which it usuallyhas a running fit such as at 21 in Fig. 3.

A proposed. arrangement consists in providing maintained between these members, in fact not a running fit. The rotor 8| has radially disposed slots 82 extending longitudinally through the -wall thereof and communicating with an axial bore 83 provided in the rotor. The rotor also has a plurality of openings 85 spaced apart and extending longitudinally between the slots 82 to lighten the structure. Blades 86' areslidably disposed in the slots 82 and are provided with laterally extending outer end portions 81 formed integral. The outer surface of the end portions 81 are formed arcuate and, due to the increased width a much more eflective surface is provided which results in less wear and longer life.

The outer end portions 81 are adapted to contact with the inner surface of the liner 88 as the rotor is rotated. Portions of the rotor adjacent the outer end portions 81 are flattened as indicated at 88.

A hollow roller member 88 is disposed in the bore 83 of the rotor and engages the inner ends of the blades 66 to maintain them in spaced relation. The inlet and outlet openings 88 provided in the liner 88 should be positioned so that there is no communication between the openings irrespective of the positions of the blades 86.

In the operation of ,the' pump assuming the rotor 26 to be rotated in a clockwise direction, as shown in Fig. 3, the opening 24 is connected by a conduit with the various instruments to be operated, while the opening 25 is connected by a suitable conduit preferably with the interior of the motor housing. The instruments, of course, a

are connected with atmosphere in the usual manner and the interior of the pump is likewise con-,

of the spring 18, the amount of movement or opening thereof being dependent uponthe pressure exerted by the spring 18. Such action creates a vacuum in the conduit leading to the instruments as the blades 36 tend to draw from the passageway I8 and discharge the air under pressure through the opening 25. The amount 01' vacuum created for the operation of the instruments should remain as nearly constant as possible throughout a wide range of engine speed. The accuracy of the instruments depends upon this amountof vacuum being as nearly constant as possible and for this reason the valve member 68 is made of non-metallic material. The

valve member, being of light weight, is therefore unaffected whether the plane is flying upside down, banking around to the right or left, or

flying right-side up. The pump has been designed and built to operate under constant conditions.

irrespective of the changes in atmospheric pres-" 1. A vacuum pump comprising a housing hav-.

ing a circular chamber therein open at one end,

said housing being further provided 'with inlet, and outlet passageways communicating with a liner 88 of the same type and character as the said chamber adapting the pump for operation in opposite directions, a tubular liner secured to the peripheral wall of said chamber and having openlet and outlet openings, a-cover plate detachably connected to said housing and adapted to close the open end of said chamber, a rotor ec- 1 centrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said inlet and outlet passageways, extensions on said rotor rotatably mounted anti-frictionally in said hous ing and cover plate respectively, one of said extensions having an axial opening communicating with an axial bore of larger diameter provided in said rotor, the other of said extensions projecting through said housing and adapted .Ior connection with a driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slidably mounted in said slots and having their outer ends in running engagement with the inner peripheral wall or said liner, and a roller member insertable through the opening in said extension and disposed in the bore' in said rotor, said roller member being normally maintained within the bore by engagement with the* adjacent end walls of said rotor bore and engageable with the inner ends of said blades to maintain thelatter in spaced relation.

2. A vacuum-pump comprising a housing having a circular chamber therein open at one end,

wall of said chamber having openings therethrough communicating with said inlet and outlet passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said inlet and outlet passageways, extensions on said rotor rotatably mounted, anti-frictionally in said housing and cover plate respectively, one of said extensions having an axial opening communicating with anaxial bore of larger diameter provided in said rotor, the'other of said extensions projecting through said housing and adapted for connection with a driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slid- V I ing a circular chamber-therein open at one end,

said housing being further provided with inlet 'and outlet passageways communicating with said chamber adapting the pump for operation inripheral wall of said liner between said inlet.

and outlet passageways, extensions on said rotor rotatably mounted anti-irictlonally in said housing and cover plate respectively, one of said extensions having an axial opening communicating with an axial bore of larger diameter pro-' vided in said rotor, the other of said extensions projecting through said housing and adapted for connection with'a driving means, said rotor be-. ing further provided with a plurality of radially disposedslots extending through the wall thereof,

blades slidably mounted in said slots and having the inner ends of said blades to maintain the v latter in spaced relation, and means provided in said housing ior'conveying a lubricant to theinterior of said hollow roller member.

4, A vacuum pump comprising a housing having a circular chamber therein open at one end, said housing being further provided with inlet and outlet passageways communicating with said chamber adapting the pump for operation in opposite directions, a tubular liner secured to the peripheral wall of said chamber and, having openings therethrough communicating with said inlet and outlet passageways, a cover plate detachably connected to said housing and adapted to close passageways, extensions on said rotor .rotatably mounted anti-frictionally in said housing and cover plate respectively, one of said extensions having anaxial opening communicating with an axial bore of larger diameter provided in said rotor, the other of said extensions projecting through said housing and adapted for connection with a'driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof and a plurality of longitudinally extending openings positioned between and substantially parallel with said slots, blades slidably mounted in said slots and having their outer ends in running engagement with the inner peripheral wall of said liner, and a roller member insertable through the opening in said extension and disposed in-the bore in said rotor, said roller member being normally maintained within the bore by engagement with the adjacent end walls of said rotor bore and engageable with the inner ends of said blades to maintain the latter in spaced relation.

5. A vacuum pump comprising a housing having a circular chamber therein open at one end, said housing being further provided with inlet and outlet passageways communicating with said chamber adapting the pump for operation in opposite directions, a tubular liner securedito the peripheral wall of said chamber and having openings therethrough communicating with said inlet and outlet passageways, a cover plate detachably connected to said housing and adapted to close the open end or said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said inlet and outlet passageways, extensions on said rotor rotatably. mounted anti-irictionally in said housing and cover plate respectively, onerof said extensions having an axial opening communicating with an axial bore of larger diameter provided in said rotor, the other of said extensions projecting through said housing and adapted for connection with a driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slidably mounted in said slots and having their outer ends in running engagement with the inner peripheral wall of said liner, said blades being provided with longitudinally extending openings, and a roller member insertable through the opening in said extension and disposed in the bore in said rotor, said roller member being normally maintained within the bore by engagement with the adjacent end walls of said rotor bore and engageable'with the inner ends of said blades connected to said housing and adapted to close the open end of said chamber, a rotor eccentricaliy positioned in said chamber and having a running engagement with-the inner peripheral wall of said liner between said inlet and outlet passageways, extensions on' said rotor rotatably mounted anti-frictionally in said housing and cover plate respectively, one of said extensions having an axial opening. communicating with an axial bore of larger diameter provided in said rotor, the other of said extensions projecting through said housing and adapted for connecliner, said blades being provided with longitudinally extending openings, and a roller member insertable through the opening in said extension and disposed in the bore in said rotor, said roller member being normally maintained within the bore by engagement with the adjacent end walls of said rotor bore and engageable with the inner ends of said blades to maintain the latter in spaced relation.

'7. A vacuum pump comprising a housing having a circular chamber therein open at one end, said housing being iurther provided with inlet and outlet passageways communicatin with said chamber adapting the pump for operation in opposite directions, a tubular liner secured to the peripheral wall of said chamber and having openings therethrough communicating with said inlet and outlet passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between'said inlet and outlet passageways, extensions on said rotor rotatably mounted anti-frictionally in said housing and cover plate respectively, one of said extensions having an axial opening communicating with an axial bore of larger diameter provided in said rotor, the other of said. extensionsprojecting through said housing and adapted for connection with a driving means, said rotor-being further provided with a plurality of radially disposed slots extending through the wall thereof and a plurality of longitudinally extending openings positioned-between and substantially parallel with said slots, blades slidably mounted in said slots and having their outer ends in running engagesaidblades being provided with longitudinally extending openings, a hollow roller member insertable through the opening in said extension and disposed in the bore of said rotor, said roller member having openings through the wall thereof and being normally maintained within the bore by engagement with the adjacent end walls of said rotor bore and engageable with the inner ends of said blades to maintain the latterv in spaced relation, and means on said cover plate for conveying a lubricant to the interior of said hollow roller member.

8. A vacuum pump comprising a housing having a circular chamber therein open at one end, said housing being further provided with inlet and outlet passageways communicating with said chamber, a tubularliner secured to the peripheral wall of said chamber and having openings therethrough communicating with said passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said passageways, said rotor having an axial bore extending inwardly from one end thereof, axial extensions on said rotor rotatably mounted antifrictionally in said housing and cover plate reinner ends projecting into the bore in' said rotor, and a roller member disposed within the bore in through the opening in one of said extensions and normally maintained within the bore by engagement .with the adjacent'end walls of the latter.

9. A vacuum pump comprising a housing having a circular chamber therein open at one end, said housing being further provided with inlet and outlet passageways communicating with said chamber, ,a tubular liner secured to the peripheral wall of said chamber and having openings therethrough communicating with said passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, said cover plate being provided with a lubricant passageway, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said passageways, said rotor having an axial bore extending inwardly from one end cover plate respectively, one of said extensionshaving an axial opening therethrough commu-' nicating with the bore in said rotor but of smaller relative diameter, the other of said extensions projecting through the adjacent wall of said housing and adapted for connection with a driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slidably mounted in said slots and having their outer ends in running engagement with the inner peripheral wall of said liner and their inner ends projecting into the bore in said rotor, and a hollow roller member disposed within thebore in said rotor and engageable with the inner ends of said blades to maintain the latter in spaced relation, said roller member being insertable through the opening in one of said extensions and normally maintained within the bore by engagement with the adjacent end walls of the latter, said roller member being provided with a plurality of openings in the wall thereof, and a tubular member having one end connected to said cover member and communicating with the lubricant passageway in the latter and its opposite end projecting freely into the interior of said hollow roller member.

10. A vacuum pump comprising a housing having a circular chamber therein open at one end,

said housing being further provided withinlet and outlet passageways communicating with said chamber, a tubular liner secured to the peripheral wall of said chamber and having openings therethrough communicating with said passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of said liner between said passageways, said rotor having an axial bore and walls at the opposite ends of said bore, said rotor being further provided with a plurality of radially disposed slots extending through the outer wall thereof, axial extensions on said rotor rotatably mounted in said housing and said cover plate respectively, one of said extensions having an axial opening therethrough communicating with the bore in said rotor but of a smaller relative diameter, the 'other of said .extensions projecting through the adjacent wall of said housing and adapted for connection with a driving means, blades slidably mounted in said slots and having their outer ends of substantially the same length as thelength of said rotorand their inner ends of substantially the same length as the length of said bore and disposed in the latter, and a roller member disposed within the bore in said rotor and vengageable with the inner ends of said: blades to maintain the latter in spaced relation, said roller member being insertable through the opening in one of said extensions and normally maintained within the bore by engagement with the adjacent end walls with the interior of said bore but of smaller relathe bore in said rotor, and a roller member disposed within the bore in said rotor and engageable with the inner ends of said blades to maintain the latter in spaced relation, said roller member being insertable through the opening in one of said extensions and normally maintained within the bore by engagement with the adjacent end walls of the latter.

12. A vacuum pump comprising a housing having a circular chamber therein and provided with inlet and outlet passageways communicating with said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of the latter between said inlet and outlet passageways, extensions on said rotor rotatably mounted in said housing, one of said extensions having an axial opening communicating with an axial bore of through the opening in said extension and disposed in the bore in said rotor, said roller member being normally maintained within the bore by engagement with the adjacent end walls'and engageable with the inner ends of said blades to maintain the latter in spaced relation,

13. A vacuum pump comprising a housing having a circular chamber therein and provided with inlet and outlet passageways communicating with said chamber, a rotor eccentrically positioned in said chamber and having a running engagement with the inner peripheral wall of the latter between said inlet and outlet passageways, extensions. on said rotor rotatably mounted in said housing, one of said extensions having an axial opening communicating with \an axial bore of, larger diameter provided in said rotor, the other of said extensions projecting through said housing and adapted for connection-with a driving means,

said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slidably mounted in said slots and'having their outer ends in runningengagement with the inner peripheral wall of said chamber, a hollow roller member insertablethrough the opening in said extension and disposed in the bore in said rotor, said roller member being normally maintained within the bore by engagement with the adjacent end walls and engageable with the inner'ends of said blades to maintain the latter in spaced relation, said housing being provided with a lubricant'passageway, and atubular extension on said housing and having one end communicating with said lubricant passageway and its otherend freely projecting into said-hollow roller member the latter provided with a plu-v rality of openings extending through the wall thereof.

14. A vacuum pump comprising a cast housing having afcircular chamber extending inwardly thereof to provide an open end, said housing hav-' ing passageways of substantially identical area .disposed upon diametrically opposite sides and extending part way around said chamber, the upper ends of said passageways being terminated by a transverse partition, said housing having inlet and outlet openings, one positioned on each side of said.

partition and communicating with the respective passageway, atubular sleeve insertable in said circular chamber and secured therein againstrelative rotation, said sleeve being in length substantially the depth of said chamber and having pairs of openings therethrough communicating with the respective passageways, the openings of each pair being positioned adjacent the ex'-- tremities of the respective passageways, a cover plate detachably connected to said housing and adapted to close the open end of said chamber, said cover plate having a portion engageable with the adjacent end of said sleeve to retain the latter within said chamber, a rotor eccentrically positioned in said sleeve and having a running engagement with the inner peripheral wall of the latter adjacent said partition, said rotor being adapted ,for rotation in either direction, axial extensions on the opposite ends of said rotor rotatably mounted in said housing and cover plate respectively, one of said extensions having an axial opening therethrough communicating with an axial bore of relatively larger diameter provided in said rotor, the other of said extensions projecting through the adjacent wall of said housing and adapted for connection with a driving means, said rotor being further provided with a plurality of radially disposed slots extending through the wall thereof, blades slidably mounted in said slots and having their outer ends in running engagement with theinner perip era1.wall of said sleeve, and a roller member insertable through the axial opening in one of said extensions and disposed in the bore in said rotor, said roller member being normally maintained'within said bore.by engagement with the adjacent end walls and engageable with the inner ends of said blades to maintain the latter in spaced relation.

JAMES P.'JOI'INSON. 

